Field of the Invention
The present invention relates to an imprint apparatus, an imprint method, and a method of manufacturing an article.
Description of the Related Art
Demand for smaller semiconductor devices, MEMS, and the like has increased, and in addition to conventional photolithography techniques, microfabrication techniques according to which uncured resin on a substrate is molded using a mold so as to form a resin pattern on the substrate have been gaining attention. This technique is called an imprint technique, and it can be used to form microstructures (patterns) on the order of several nanometers on a substrate. Photocuring is one example of an imprint technique.
With an imprint apparatus that uses photocuring, first, photocurable resin (ultraviolet-curable resin) is supplied (applied) to a shot region (imprinting region) of a substrate and the resin (uncured resin) is molded using a mold. Then, light (ultraviolet ray) is emitted so as to cure the resin and the mold is removed from the cured resin on the substrate, and thereby a pattern of resin is formed on the substrate.
In a manufacturing step for a device, for example, since the substrate that is to be targeted to imprint process undergoes a heating process in a layer-forming step such as sputtering, there are cases where the entirety of the substrate expands or contracts and the shape (size) thereof changes in two axial directions that are perpendicular in a plane. Accordingly, with an imprint apparatus, when a mold is pressed onto the resin on the substrate, the shape of the pattern formed on the substrate (substrate side pattern) and the shape of a pattern formed on the mold (mold side pattern) need to be aligned. In the case of using an exposure apparatus, this kind of shape correction (magnification correction) can be dealt with by changing the demagnification of a projection optical system or the scanning velocity of a substrate stage according to the magnification of the substrate so as to change the image size. In contrast to this, an imprint apparatus includes a shape correction mechanism (magnification correction mechanism) that causes a mold to physically deform by applying an external force from a side surface of the mold or applying heat to the mold.
Herein, a case will be considered in which an imprint apparatus is applied in a step of manufacturing a semiconductor device with a half pitch of around 32 nm, for example. In this case, according to ITRS (International Technology Roadmap for Semiconductors), the overlay precision is 6.4 nm. Accordingly, in order to comply with this feature, shape correction also needs to be performed at a precision of several nanometers or less.
On the other hand, there is a possibility that deformation (distortion) will occur also in a mold used in the imprint apparatus. For example, during manufacturing, the pattern surface of the mold is oriented upward, and during use, the pattern surface of the mold is oriented downward. Accordingly, when using a mold, there is a possibility that the pattern surface (mold side pattern) will deform due to the influence of gravity, and the like. Also, since a mold pattern is generally formed by a drawing apparatus using a charged particle beam (electron beam, etc.), there is a possibility that a distortion will be generated in the pattern due to a distortion or the like of the optical system of the drawing apparatus.
Japanese Patent Laid-Open No. 2010-080714 proposes a technique for improving the overlay precision by aligning the shape of the substrate side pattern and the shape of the mold side pattern. With the technique disclosed in Japanese Patent Laid-Open No. 2010-080714, the substrate side pattern and the mold side pattern are aligned by causing the mold to deform using a mold chuck that holds the mold. Also, Japanese Patent Laid-Open No. 2007-137051 proposes a technique for aligning the mold and the substrate. With the technique disclosed in Japanese Patent Laid-Open No. 2007-137051, when the mold and the substrate are to be aligned while the mold and the resin on the substrate are in contact, the pressure applied by the mold on the resin is reduced, thereby facilitating adjustment of the positional relationship between the mold and the substrate.
With an imprint apparatus, accompanying a reduction in the size of the pattern formed on the substrate, the thickness of the resin (residual layer) during imprint process needs to be made thin for an etching process in a later step. Accordingly, during molding of the resin, resin of a thickness of several tens of nanometers or less is sandwiched between the mold and the substrate. It is known that liquid interposed in a microscopic gap of this order undergoes structuration and has high viscoelastic properties.
If the mold and the substrate are moved relative to one another for alignment while the mold and the resin on the substrate are in contact (while the resin is sandwiched between the mold and the substrate), a force corresponding to the viscoelasticity of the resin is applied to the mold and the substrate in a shearing direction (direction parallel to contact surface). Also, if a foreign particle is sandwiched between the mold and the substrate, the mold and the substrate will become engaged due to the foreign particle, and as described above, a force in the shearing direction will be applied to the mold and the substrate.
Due to the force in the shearing direction, a shearing force is generated in the mold or the substrate, which causes deformation. Accordingly, a relative shape difference between the mold side pattern and the substrate side pattern will occur. In other words, if a shearing force is generated in the mold or the substrate during alignment of the mold and the substrate, the shape of the mold side pattern and the shape of the substrate side pattern will change relative to each other and the overlay precision between the mold side pattern and the substrate side pattern will decrease.